Extracting metals and equilibria Study Guide

The method used to extract a metal from its ore is directly linked to the metal's position in the reactivity series. Metals that are less reactive than carbon, such as iron, can typically be extracted from their oxides by heating with carbon. Carbon is more reactive than these metals, so it displaces them from their compounds, reducing the metal oxide to the pure metal and forming carbon dioxide. In contrast, highly reactive metals, like aluminium, are more reactive than carbon. This means carbon cannot displace them from their oxides. For these metals, a more energy-intensive and costly method, such as electrolysis, is required. Electrolysis involves passing an electric current through a molten compound of the metal, splitting it into its constituent elements. The significant energy requirement for heating substances to a molten state and maintaining the electric current makes electrolysis a much more expensive process than heating with carbon. Therefore, the choice of extraction method is a compromise between the reactivity of the metal and the economic viability of the process.

Most metals are extracted from naturally occurring compounds called ores, which are found within the Earth's crust. These ores are typically metal oxides, sulfides, or carbonates. The process of extracting the metal from its ore often requires significant energy and chemical reactions, such as reduction, to separate the pure metal. However, some metals are so unreactive that they do not readily form compounds with other elements. These unreactive metals, such as gold and platinum, are found in the Earth's crust as uncombined elements, meaning they exist in their pure metallic form and do not require chemical extraction processes from ores. Their extraction primarily involves physical separation from surrounding rock.